Yeah I put it on youtube originally but it takes sometime to go public...VIDEO Kenny,
I know you are making some headway, but I found this write up on LNF Performance about a similar code and noise to what you were describing: It's a long read, but helpful.
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DTC P2261
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P2261: Turbocharger Bypass Valve Stuck Closed
System Description
The BorgWarner™ dual-scroll turbocharger (TC) incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a PWM solenoid, in order to regulate the pressure ratio of the compressor. A charge air bypass valve is integrated within the unit, and is also controlled by the ECM by utilizing a remotely mounted solenoid to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the valve is commanded open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the TC and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command, the valve will then close to optimize TC response.
Front wheel drive platforms also incorporate a charge air bypass valve vacuum tank. The purpose of the tank is to provide an instant source of vacuum to the bypass valve, when it is commanded open by the ECM. This results in less pressure buildup under closed throttle conditions, thereby reducing compressor noise and surge.
The purpose of this diagnostic is to determine if the charge air bypass valve is stuck closed. The ECM will first verify the integrity of the following sensors. The ECM then compares the actual measured mass air flow (MAF) to a modeled airflow that is derived from these inputs:
• Throttle position (TP)
• Engine speed
• Intake air pressure sensor
• Manifold absolute pressure (MAP) sensor
Conditions for Running the DTC
• DTCs P0033, P0034, P0035, P0096, P0097, P0098, P0099, P0100, P0101, P0102, P0103, P0106, P0107, P0108, P0121, P0122, P0123, P0221, P0222, P0223, P0234, P0236, P0237, P0238, P0299, P2227, P2228, or P2229, is not set.
• The boost pressure versus the BARO pressure ratio is between 1.1-3.3.
• The charge air bypass valve has been commanded ON for greater than 1 second immediately after an abrupt closed throttle has occurred and the resulting pressure ratio across the compressor exceeds the calibrated pressure ratio limit.
• The battery voltage is between 10-18 volts.
• This DTC runs continuously within the enabling conditions.
Conditions for Setting the DTC
The ECM by comparing the measured MAF to the modeled MAF has detected a series of pulsations in the induction system that exceed a calibrated threshold.
Action Taken When the DTC Sets
DTC P2261 is a Type B DTC.
Conditions for Clearing the MIL/DTC
DTC P2261 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
• Turbocharger System Description
• Boost Control System Description
Electrical Information Reference
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information.
Circuit/System Verification
Verify that DTC P0033, P0034, or P0035 is not set.
⇒ If any of the DTCs are set, refer to DTC P0033, P0034, or P0035.
Use the scan tool output controls to command the TC Bypass Solenoid ON and OFF. An audible click should be heard and felt.
⇒ If the click is not heard or felt, refer to DTC P0033, P0034, or P0035.
Set up the scan tool for a snapshot of the induction data list. With the emergency brake on, the vehicle transmission in neutral, and the engine idling, perform a wide open throttle and then quickly release the accelerator. Review the Boost Pressure Sensor parameter. There should not be any abnormal pulsations of the parameter.
With the parking brake ON and the engine idling in neutral, perform an audible test of the valve by depressing the throttle wide open, then quickly releasing it to a closed throttle position. A valve that is stuck shut will generate a turkey gobble sound. There should not be any unusual noise.
⇒ If there is unusual noise, refer to Turbocharger Cleaning and Inspection.
Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
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Chris White
2006 Spice Red A4 GTO
2008 Trailblazer SS
2008 Malibu LT2 3.6L
2009 Cobalt SS
2009 G8 GXP M6
2008 CTS4 3.6L DI
2008 CBR600RR
